A hose clamp is already known, particularly by U.S. Pat. No. 2,522,494 and DE-A-41.08,852 or by published International Applications W080/01199 and W087/00602, which is constituted by a band of flexible material, generally metal, wound on itself. One of the ends of the band presents, at least on its outer surface, a regular succession of crests and/or troughs forming a rack. On the other end of the band is fixed a housing essentially presenting two lateral sides and constituting the support of a screw which is mounted to pivot about its axis. This latter is itself substantially parallel to the longitudinal direction of the band, i.e. to a tangent to the clamp when the band is wound on itself. The longitudinal position of the screw with respect to the housing is variable and determined by at least one stop, axially mobile with respect to the housing, against the action of a spring. On this stop there abuts an appropriate zone of the tail of the screw. In certain cases, the screw is held in the housing thanks to an approximately cylindrical shape of the latter; in other cases, two bearings may be provided, receiving the threaded shank of the screw, respectively near its head and its tail.
Finally, the housing presents a transverse slot via which penetrates the free end of the band whose relief elements come into mesh with the threads of the screw, this allowing the band to be tightened by rotation of the screw with the aid of an appropriate tool.
This type of clamp incorporating tightening screw is much used in industry, particularly if it is desired automatically to compensate a possible reduction in the diameter of the object tightened, but it generally presents at least one serious drawback.
In fact, the known clamps do not allow the clearances to be taken up at the moment of tightening; in certain cases, it may be observed that the threads of the screw are disengaged from the rack of the band, thus preventing continued tightening of the clamp.
It is an object of the present invention to provide a hose clamp incorporating tightening screw of the type which has just been recalled, whose design avoids the drawback which has been set forth hereinbefore.